1. Field of the Invention
This invention relates to an integrated semiconductor laser device with a plurality of laser device elements, at least one of which has a portion for preventing the injection of current in the vicinity of one facet or both facets.
2. Description of the Prior Art
Semiconductor laser devices that are used as a light source for the optical pick up of a magnetooptical disc system or the like must operate at a low output power of about 3 mW at the time of reading of signals and at a high output power of 30 mW or more at the time of writing and erasing of signals. Moreover, upon writing of the signals, they must check on the written information. Accordingly, it is preferable that a high output power semiconductor laser device used for the writing of information and a low output power semiconductor laser device used for the reading of information are integrated in a single optical system. A plurality of the same semiconductor laser devices are generally produced at the same time by liquid phase epitaxy, metal organic-chemical vapor deposition, molecular beam epitaxy, or the like. However, when high output power semiconductor laser devices are produced, in order to prevent breakage of the facets thereof, the active layer must be made thin in the vicinity of the facets and/or layers with large energy gaps are required, which causes difficulties in the simultaneous production of these devices. Moreover, there are differences in optical characteristics such as astigmatism, light-emitting angles, or the like between the low output power semiconductor laser devices and the high output power semiconductor laser devices, so that both kinds of semiconductor laser devices cannot be used in the same optical system, causing difficulties in the integration thereof. To overcome this problem, high output power semiconductor laser devices are used as substitutes for low output power semiconductor laser devices, or high output power semiconductor laser devices and low output power semiconductor laser devices that are separately produced are mounted on a single stem. To operate a high output power semiconductor laser device at a low output power level is inefficient. Moreover, when the two laser devices that are separately produced are mounted on a single stem, the facets of one laser device must agree with those of the other laser device, which necessitates excessive technical skill.